The production of workpieces used in the magnetic disc drive industry begins with the creation of a substrate with a hard smooth surface upon which magnetic material can be deposited. A hard smooth surface may be formed by coating a relatively soft material such as aluminum with a relatively hard material such as nickel. The hard material is polished to a smooth finish, and magnetic material is then deposited onto the polished surface of the workpiece. Several methods for depositing magnetic material onto the polished surface can be used; for example, electro-deposition and sputtering are two well known methods.
After polishing, the workpieces are typically cleaned prior to the deposition of magnetic material. If the surface of the workpiece is contaminated with debris from the polishing process or elsewhere, the adherence of the magnetic material to the surface of the workpiece will be imperfect, and "blisters" of missing magnetic material may form on the surface of the workpiece. These "blisters" create areas on the completed magnetic disc that are incapable of storing information. Similarly, in optical disc manufacturing, debris on the surface of the workpiece may cause voids in information storage. In semiconductor wafer manufacturing, debris may attach to the surface of the workpiece, causing defects on the surface of the workpiece. These defects can cause electrical shorts or other problems within the microelectronic structures on the workpiece. Accordingly, it is often important to clean the workpieces to remove debris from the corresponding surfaces.
Contact scrubbing with sponge-like material is one method used to remove debris from the surface of the workpiece. A typical prior art cleaning element used for contact scrubbing of workpieces is described in U.S. Pat. No. 5,311,634, issued May 17, 1994 to Andros. A conventional cleaning element 10 may be configured as shown in FIG. 1. Cleaning element 10 generally includes a sponge-like cleaning material 12 and a core 14. Cleaning material 12 is formed over core 14 and seals with itself at an outer edge 16 of core 14. Cleaning material 12 may be made of a variety of resilient materials, including polyvinyl alcohol and urethane. As with other prior art cleaning elements, cleaning material 12 may have bumps or other texturing on its outer surface to facilitate effective cleaning and flushing of the workpiece surface. The arrangement of such bumps or texturing may be random or patterned. Random texturing may not provide a suitable cleaning or wiping action and some patterned cleaning elements may merely redistribute debris from one location on the workpiece to another without effectively removing the debris.
Conventional cleaning elements often utilize a relatively heavy and expensive metal or stamped plastic or polyvinyl chloride (PVC) for core 14. Unfortunately, PVC may leech chemicals or particulate into the cleaning environment during use. Such leeching is undesirable in many delicate applications. In addition, some conventional cleaning elements utilize a permanent core 14 that is designed for use with disposable sponge elements. Such an arrangement is inconvenient to maintain and requires a considerable amount of downtime to replace old sponges with new sponges.
Core 14 has a centrally located aperture 18 to allow mounting of cleaning element 10 onto a rotatable drive shaft 20. Core 14 may also have two keyways 22 and 24 formed within aperture 18 and configured to receive a single key 26 located on drive shaft 20. Key 26 and keyways 22 and 24 enable drive shaft 20 and cleaning element 10 to rotate as a single unit. Prior art cleaning element 10 uses such multiple keyways 22, 24 to facilitate adjustable alignment of the texture pattern on cleaning material 12. For example, cleaning elements 10 are typically installed onto drive shaft 20 using alternating keyways 22, 24 to stagger the respective texture patterns. Unfortunately, such an alternating configuration requires additional installation time and increases the likelihood of an improper installation.
Prior art cleaning machines may employ a plurality of cleaning elements 10 to simultaneously process a plurality of workpieces. When multiple cleaning devices 10 are placed on drive shaft 20, a number of spacers 28 are often interposed between adjacent cleaning devices 10 to ensure substantially identical spacing between all cleaning devices 10. Unfortunately, installing spacers 28 onto drive shaft 20 is time consuming and labor intensive. Spacers 28 also tend to wear and become contaminated, causing nonuniform spacing between and misalignment of cleaning devices 10. Such inconsistencies may cause unpredictable processing from workpiece to workpiece.